1. Field of the Invention
The present invention relates to a process for growing gallium arsenide (GaAs) on a silicon (Si) substrate.
2. Description of the Related Art
Gallium arsenide has a high carrier mobility, and thus is very useful for semiconductor devices. However, a GaAs layer is grown on a GaAs substrate, and it is difficult to manufacture GaAs substrates having a large diameter, which is disadvantageous with regard to through-put, and therefore, there is a need to develop a technique of growing a GaAs layer on an Si substrate. This, however, leads to the problems of a large lattice mismatch, a difference of the thermal expansion coefficients of GaAs and Si, and the existence of an antiphase domain.
The problem of the presence of an antiphase domain can be solved by using offset-angle substrates, but the problems relating to warping of the substrate due to the different thermal expansion coefficients of GaAs and Si remain unsolved.
In an effort to reduce warping, it has been proposed to grow a GaAs layer on an Si substrate using a buffer layer of GaP to GaAsP to GaAs in which the lattice constant is changed from that of GaP or Si to that of GaA, through intermediate lattice constant thereof. This process, however, requires a high temperature metal organic chemical vapor deposition (MOCVD) and presents difficulties when using molecular beam epitaxy (MBE).
Therefore, an object of the present invention is to provide a GaAs layer grown on an Si substrate and a process for growing a GaAs layer on an Si substrate, whereby an excellent quality GaAs layer free of warping is formed.